1. Field of the Invention
The present invention relates to a forgery-preventive fretwork paper which is suitable for use in traveler's checks, securities, ID cards, passports, and the like which all are less forgeable.
2. Discussion of the Background
Traveler's checks, securities, and ID cards are required to be less forgeable. Forgery-preventive techniques for these have included the following.
Group I:
(1) To use a print containing a fluorescent substance therein. PA1 (2) To print with a magnetic ink to enable any change in ink density to be visually recognized based on a magnetic function. PA1 (3) To print with a printing ink containing a photochromic dye (see JP-A-60-79992; the term "JP-A" as used herein means an "unexamined published Japanese patent application"). PA1 (4) To print with an ink having specific reflection-spectroscopic properties or with two or more inks which differ from each other in reflectance by at least a given value. PA1 (5) A print produced overprinting of drawing line which changes angle drawing line and consists of 10,000 lines of colorless transparent ink for concave printing after ink drying is complete (see JP-A-5-177919). PA1 (6) To form an appearance which enables forgery detection, as in a print bearing a fretwork (latent image) (see JP-A-6-15794). PA1 (7) A print having a device which makes the characters and designs on copies thereof difficult to interpret or which produces a warning mark on copies thereof (see JP-A-U-59-64271; the term "JP-A-U" as used herein means an "unexamined published Japanese utility model application"). PA1 (8) A print obtained with a special magnetic ink so that mere copies of the print can be revealed as fakes by a discriminator, or a print bearing halftone dots so that copies of the print differ from the original in dot density (see JP-B-56-19273 and JP-B-2-51742; the term "JP-B" as used herein means an "examined Japanese patent publication"); and a print bearing concealed characters which cannot be read with the naked eye but are readable by a discriminator (see JP-A-62-130874). PA1 (1) an opacity (JIS P-8138) of from 50 to 100% and PA1 (2) a density (JIS P-8118) of from 0.70 to 1.4 g/cm.sup.3, and said paper bearing an engraving extending into said engraving coating layer or to one of said uniaxially stretched films of said support layer.
Group II:
Group III:
The forgery-preventive techniques given above in Groups I to III each is not a perfect forgery-preventive measure because most of the originals produced using these techniques can be copied by photolithography. The prior art techniques further have a drawback that since the printed characters or images peel off during the use of real checks or securities due to the poor adhesion of the printing ink to the sheet base and such checks or securities are sometimes misjudged to be fakes. It is therefore necessary to collect such real checks or securities and exchange them for fresh ones. In addition, even real checks or securities rumple during use, and the rumpled checks or securities are often rejected by a discriminator.
On the other hand, a fretwork paper comprising a support layer and an engraving layer is disclosed in JP-B-8-13539, which is characterized in that the support layer has an opacity of 70% or lower and the engraving layer has an opacity of 40% or higher, the opacity of the support layer being always lower than that of the engraving layer by at least 30%, and that an engraving is formed therein which extends from the engraving layer to the support layer. This prior art fretwork paper is advantageous in that discrimination is easy, and that the paper is effective in forgery prevention because the paper, in which the support comprises a transparent poly(ethylene terephthalate) film coated on each side with a pigmented coating layer and the engraving layer comprises a pigmented coating layer, is not easily available because of the complicated process for producing the same. However, the above fretwork paper has drawbacks that the resin film as the support is apt to develop burrs (whiskers) upon engraving, and that the paper is apt to rumple during paper feed or discharge or during use.
An object of the present invention is to provide a forgery-preventive fretwork paper which comprises a support layer and an engraving coating layer, and in which the drawbacks described above are mitigated by using a specific stretched laminate as the support layer.